This invention relates to eye surgery and more particularly to aids for retinal detachment surgery.
The retina is a thin sheet of light sensitive nerve tissue lining the inner posterior of the eye and which functions to capture focused images like the film of a camera. Retinal detachment (RD) occurs when the retina separates from the posterior wall of the eye. It is usually caused by a break in the retina. Retinal detachment is one of the major human eye diseases which can lead to severe visual impairment or even blindness unless it is treated surgically.
Scleral buckling surgery is one of the most commonly performed surgical operations to treat retinal detachment. In the surgery as conventionally practiced, silicone rubber explants are sewed externally onto the scleral tissue (eye walls) overlying the retinal tear. The explants indent the sclera against the retina and close retinal tear by relieving the force tracking on the tear. These explants are known as scleral buckles. Scleral buckles are provided in a variety of sizes and shapes to treat different sizes of retinal breaks. Usually, a long silicone strip known as encircling band is also sutured and tightened onto the globe of the eye to further relieve forces pulling up the retina from the posterior wall. To complete the surgery, cryotherapy is applied externally to achieve a permanent adhesion between the retina and underlying tissue, to prevent the retina from re-detachment.
Commercially available buckle and encircling bands are still used according to a method based on an invention by Custodis in the early 1950s (Custodis E. “Treatment of retinal detachment by circumscribed diathermal coagulation and by scleral depression in the area of tear caused by imbedding of a plastic implant,” Klin Monatsbl Augenheilkd 1956; 129:476-495). The major differences from the original invention are the material used and the configurations of the buckles. The material used is either a silicone sponge which was pioneered by Lincoff et al. (Lincoff H A, Baras I, McLean J., “Modifications to the Custodis Procedure for Retinal Detachment,” Arch. Ophthalmol. 1965; 73:160-163) or a solid silicone element which was pioneered by Schepens (Schepens C L, Okamura I D, Brockhurst R J, Regan C D, “Scleral buckling procedures v. Synthetic sutures and silicone implants,” Arch. Ophthalmol. 1960; 64:868-881). The method of securing the scleral buckle and encircling band onto the scleral wall by suturing has remained virtually unchanged for more than 50 years.
Although scleral buckling surgery is effective, it is also a highly demanding surgical procedure with potential major complications. For example, the buckle and encircling band are conventionally sutured onto the sclera with a fine needle, and the suture depth is aimed at the half thickness of the very thin sclera (0.5-1 mm). If the placement of needle is too deep, the sclera will be accidentally perforated. Perforation of sclera may damage the underlying tissue, leading to bleeding or retinal hole formation, surgical failure and permanent damage. However, if the placement of the needle is too shallow, the buckle or encircling band could be loosened or even exposed out from the eye after the surgery. A loosened or exposed buckle also leads to surgical failure, infection and unwanted pain.
Apart from perforation of the globe, suturing poses at least one more disadvantage. For securing one suture, there are two bites: the anterior anchor and the posterior anchor. The anterior anchor site is relatively easy to reach. However, the posterior anchor is usually located posterior to the equator of the globe, and this location is relatively difficult to reach. The working space for making the posterior anchor is usually very limited because of the funnel shape of the bony orbit and the posterior location of the anchor site. Sometimes the surgeon must pull the extra-ocular muscle with a bridle suture in order to rotate the eye ball to yield more working space for applying the suture. The patient may experience great pain during this step and sometimes patient's heart rate may be decreased because of oculo-cardic reflex. Moreover, the posterior anchor can be located close to the exit of the vortex vein. If the vortex vein is accidentally perforated, profound bleeding can lead to failure of the whole surgery.
U.S. Pat. No. 4,299,227—Ophthalmologic appliance of Lincoff describes a method of treating retinal detachments through a small conjunctival incision wherein an expandable balloon like device is inserted into Tenon's space of the eye. The balloon is then expanded, to form a temporary indentation in the eye, and the balloon is deflated and removed from the eye after the retina has re-attached. There is no permanent indention effect onto the retina because the balloon is removed from the eye once the retina is re-attached in the early postoperatively period. The retinal detachment has higher chances of re-detaching when the indentation is removed, especially when there is proliferative vitreo-retinopathy during mid or late postoperative period.
U.S. Pat. No. 4,452,776—Hydrogel implant article and method of Refojo describes a hydrogel buckle of significant softness, pliability and elasticity when dry as well as when wet. It is sutured onto the scleral wall to produce the indentation effect. It claimed to be better than silicone in that it will swell up post-operatively to give a greater indentation effect. However, it can swell unexpectedly up to four fold of its original size years after the surgery because of hydrolytic degradation, thus potentially causing serious complications such as buckle extrusion, intrusion, squint and subcutaneous mass, etc. Production of this device was halted in mid 90's.
U.S. Pat. No. 6,547,714—Magnetized scleral buckle for use with silicone magnetic fluids in the treatment of retinal diseases, and U.S. Pat. No. 6,135,118—Treatment with magnetic fluids, both by Dailey describe a method to treat retinal detachment by the combined usage of a magnetic fluid tamponade inside the eye with a magnetized flexible scleral buckle placed outside the eye. The magnetic fluid is injected into the eye using a syringe, and the magnetic scleral buckle is positioned and immobilized in place, generally by suture or adhesive. The scleral buckle needs to be fixed in place by sutures or adhesives, which inevitably pose the same hazards as conventional scleral buckling surgery.
U.S. Patent Publication US2006/06167422 A1-Heat shrink scleral band with custom-made buckle for retinal detachment surgery of Mohsen Shahinpoor et al. discloses a scleral band of polymeric material that is capable of shrinking when it is stimulated by heat (hot-tip), laser, radio-frequency or other conventional means. In the Shahinpoor system, a progressively increasing indention effect is created by the progressive tightening of the scleral band. It is noted that the system requires a number of stages of follow-up procedures to produce the progressively increasing indention effect. The scleral band is inserted into the Tenon's space, but there is no mechanism described to stabilize the scleral band onto the eyeball. There is no external drainage of subretinal fluid. It aims at internal self-absorption of subretinal fluid. The ends of the scleral band are joined together by self-locking serrated ends. The scleral band can be combined with one snap-on custom-made buckle by an insertion peg to achieve scleral indention over the retinal tear region. The invention aims at merely a temporary indention (at least three days) and the whole implant is designed to be removed from the eye when the retina is re-attached.
If scleral buckling surgery can be improved, the risk is much reduced and the success rate is increased.